Bounce Rate in SEO is called as a percentage of visitors who only visits one page of your website or leave the website without signup, clicking on the other pages, making any purchase, etc. Bounce Rate is also considered as a google ranking factor. It is considered that the average bounce rate should be within 41% to 51%. Bounce rate more than 51% is considered as a bad bounce rate which indicates a bad user experience and poor quality of content on the website.
To reduce bounce rate, you need to re-work on content(make it easy to read) present on the website, check for the page loading speed, used compressed images on the website, etc.